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Receiver-operating Characteristic (receiver-operating + characteristic)

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Medical Sciences77%

Terms modified by Receiver-operating Characteristic

  • receiver-operating characteristic curve
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    Selected Abstracts

    A System for Grouping Presenting Complaints: The Pediatric Emergency Reason for Visit Clusters

    ACADEMIC EMERGENCY MEDICINE, Issue 8 2005
    MSCE, Marc H. Gorelick MD
    Abstract Objectives: To develop a set of chief complaint groupings for pediatric emergency department (ED) visits that is comprehensive, parsimonious, clinically sensible, and evidence-based. Methods: Investigators derived candidate chief complaint clusters and ranked them a priori into three perceived severity categories. Pediatric visits were extracted from the National Hospital Ambulatory Medical Care Survey (NHAMCS); data for years 1998 and 2000 (n= 13,186) were used for derivation and data for year 1999 (n= 5,365) were used for validation. Visits were assigned to clusters based on the recorded complaints; clusters were combined to ensure adequate numbers for analysis (minimum n= 20), and the clusters were reviewed for clinical sensibility. Resource utilization was categorized in three levels: routine (examination only), ED treatment (tests or therapy in the ED but not admitted), and admission. Area under the receiver-operating characteristic (ROC) curve (AUC) was used to demonstrate the discriminative ability of the clusters in predicting resource use. Results: There were 463 unique complaints in the derivation database; 95 (20%) had a single associated visit. Fifty-two clusters were generated; only 2.4% of complaints were classified as other. The eight most common clusters encompassed 52% of the visits. The top five were fever (11%), extremity pain/injury, vomiting, cough, and trauma (unspecified). Complaint clusters were associated with actual resource utilization: for routine care, the AUC was 0.73 (0.74 in the validation set), and for admission, the AUC was 0.77 (0.74 in the validation set). Both resource utilization and triage classification increased with increased expert severity ranking (test for trend, p < 0.001). Conclusions: The proposed Pediatric Emergency Reason for Visit Cluster (PERC) system is a comprehensive yet parsimonious, clinically sensible means of categorizing pediatric ED complaints. The PERC system's association with measures of acuity and resource utilization makes it a potentially useful tool in epidemiologic and health services research. [source]

    What changes in health-related quality of life matter to multiple myeloma patients?

    EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2010
    A prospective study
    Abstract Objective: To determine the clinical significance of changes in quality-of-life scores in patients with multiple myeloma (MM), we have estimated the minimal important difference (MID) for the health-related quality-of-life instrument, the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30. The MID is the smallest change in a quality-of-life score considered important to patients. Methods: Between 2006 and 2008, 239 patients with MM completed the EORTC QLQ-C30 at inclusion (T1) and after 3 months (T2). At T2, a structured quality-of-life interview was also performed. MIDs were calculated by using mean score changes (T2,T1) for patients who in the interview stated they had improved, deteriorated or were unchanged. MIDs were also estimated by the receiver-operating characteristic (ROC) curve method as well as by calculation effect sizes using standard deviations of baseline scores. Results: MIDs varied slightly depending on the method used. Patients stating in the interview that they had ,improved' or ,deteriorated' had a corresponding change in EORTC QLQ-C30 score ranging from 6 to15 (improvement) and from 9 to17 (deterioration) (scale range 0,100). The ROC analysis indicated that changes in score from 7 to17 represent clinically important changes to patients. The effect size method suggested 5,6 to be a small and 11,15 to be a medium change. Conclusion: Calculation of MIDs as mean score changes or by ROC analysis suggested that a change in the EORTC QLQ-C30 score in the range of approximately 6,17 is considered important by patients with MM. These MIDs are closer to a medium effect size than to a small effect size. Our findings imply that mean score changes smaller than 6 are unlikely to be important to the patients, even if these changes are statistically significant. [source]

    The number of CD34+ cells in peripheral blood as a predictor of the CD34+ yield in patients going to autologous stem cell transplantation

    JOURNAL OF CLINICAL APHERESIS, Issue 2 2006
    A.L. Basquiera
    Abstract The number of CD34+ cells in peripheral blood (PB) is a guide to the optimal timing to harvest peripheral blood progenitor cells (PBPC). The objective was to determine the number of CD34+ cells in PB that allows achieving a final apheresis product containing ,1.5 × 106 CD34+ cells/kg, performing up to three aphereses. Between March 1999 and August 2003, patients with hematological and solid malignancies who underwent leukapheresis for autologous bone marrow transplantation were prospectively evaluated. Seventy-two aphereses in 48 patients were performed (mean 1.45 per patient; range 1,3). PBPC were mobilized with cyclophosphamide plus recombinant human granulocyte-colony stimulating factor (G-CSF) (n = 40), other chemotherapy drugs plus G-CSF (n = 7), or G-CSF alone (n = 1). We found a strong correlation between the CD34+ cells count in peripheral blood and the CD34+ cells yielded (r = 0.903; P < 0.0001). Using receiver-operating characteristic (ROC) curves, the minimum number of CD34+ cells in PB to obtain ,1.5 × 106/kg in the first apheresis was 16.48 cells/,L (sensitivity 100%; specificity 95%). The best cut-off point necessary to obtain the same target in the final harvest was 15.48 cells/,L, performing up to three aphereses (sensitivity 89%; specificity 100%). In our experience, ,15 CD34+ cells/,L is the best predictor to begin the apheresis procedure. Based on this threshold level, it is possible to achieve at least 1.5 × 106/kg CD34+ cells in the graft with ,3 collections. J. Clin. Apheresis 2005. © 2005 Wiley-Liss, Inc. [source]

    A further investigation on a MALDI-based method for evaluation of markers of renal damage

    JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2009
    Annunziata Lapolla
    Abstract The validity of the urinary protein profile to characterize the pathological states of diabetic, nephropathic and diabetic,nephropathic patients was considered on the basis of previously obtained results by MALDI/MS, showing a different abundance ratio of the collagen ,1 and ,5 chain precursor fragments at m/z 1219 and 2049 and of the uromodulin precursor fragment at m/z 1912 observed in healthy subjects and patients; a larger number of subjects was examined and the obtained results were statistically evaluated. The p values related to the observed differences indicate that they are statistically significant when comparing all patients versus healthy controls, diabetic with normo or microalbuminuria versus nephropathic with advanced renal disease patients and diabetic with normo or microalbuminuria versus diabetic with advanced nephropathy patients. The scatter plot matrix gives evidence of the strict inverse relationship between the abundances of ions at m/z 1912 and 1219, the correlation coefficient being particularly high (r = 0.921, p < 0.001). The relationship between the true positive rate (sensitivity) and false positive rate (1,specificity) for every possible cutoff value in abundance of the considered ionic species was investigated through the receiver-operating characteristic (ROC) curve. The obtained data indicate that a good differentiation of nephropathic patients with advanced renal disease and diabetic patients with advanced nephropathy versus healthy subjects can be easily obtained by this approach. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Utility of the distal compound muscle action potential duration for diagnosis of demyelinating neuropathies

    JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 3 2009
    Sagiri Isose
    Abstract To assess the significance of distal compound muscle action potential (CMAP) duration for diagnosis of demyelinating neuropathies, electrophysiologic data were reviewed from 471 subjects, including 145 normal controls, 60 patients with chronic inflammatory demyelinating polyneuropathy (CIDP), 205 with other neuropathy, and 61 with amyotrophic lateral sclerosis (ALS). The duration of distally evoked CMAP was measured in the median, ulnar, tibial, and peroneal nerves. Optimal cut-off values were calculated with receiver-operating characteristic (ROC) curves. In comparison of normal controls and CIDP patients, ROC analyses showed the sufficient area under the curves (82-93%). When the cut-off values in the detection of demyelination were determined as the point with 98% specificity vs. normal on the ROC curves (median, 6.6 ms; ulnar, 6.7 ms; peroneal, 7.6 ms; tibial, 8.8 ms), the sensitivity was 77% for CIDP, with a specificity of 90% vs. ALS and 95% vs. diabetic neuropathy. The distal CMAP duration is a useful index for the detection of distal demyelination. We suggest the above cut-off values for each nerve as one of the electrodiagnostic criteria for demyelinating neuropathies, preferentially affecting the distal nerve terminals, such as CIDP. [source]

    Estimation methods for time-dependent AUC models with survival data

    THE CANADIAN JOURNAL OF STATISTICS, Issue 1 2010
    Hung Hung
    Abstract The performance of clinical tests for disease screening is often evaluated using the area under the receiver-operating characteristic (ROC) curve (AUC). Recent developments have extended the traditional setting to the AUC with binary time-varying failure status. Without considering covariates, our first theme is to propose a simple and easily computed nonparametric estimator for the time-dependent AUC. Moreover, we use generalized linear models with time-varying coefficients to characterize the time-dependent AUC as a function of covariate values. The corresponding estimation procedures are proposed to estimate the parameter functions of interest. The derived limiting Gaussian processes and the estimated asymptotic variances enable us to construct the approximated confidence regions for the AUCs. The finite sample properties of our proposed estimators and inference procedures are examined through extensive simulations. An analysis of the AIDS Clinical Trials Group (ACTG) 175 data is further presented to show the applicability of the proposed methods. The Canadian Journal of Statistics 38:8,26; 2010 © 2009 Statistical Society of Canada La performance des tests cliniques pour le dépistage de maladie est souvent évaluée en utilisant l'aire sous la courbe caractéristique de fonctionnements du récepteur (, ROC , ), notée , AUC , . Des développements récents ont généralisé le cadre traditionnel à l'AUC avec un statut de panne binaire variant dans le temps. Sans considérer les covariables, nous commençons par proposer un estimateur non paramétrique pour l'AUC simple et facile à calculer. De plus, nous utilisons des modèles linéaires généralisés avec des coefficients dépendant du temps pour caractériser les AUC, dépendant du temps, comme fonction des covariables. Les procédures d'estimation asociées correspondantes sont proposées afin d'estimer les fonctions paramètres d'intérêt. Les processus gaussiens limites sont obtenus ainsi que les variances asymptotiques estimées afin de construire des régions de confiance approximatives pour les AUC. À l'aide de nombreuses simulations, les propriétés pour de petits échantillons des estimateurs proposés et des procédures d'inférence sont étudiées. Une analyse du groupe d'essais cliniques sur le sida 175 (ACTG 175) est aussi présentée afin de montrer l'applicabilité des méthodes proposées. La revue canadienne de statistique 38: 8,26; 2010 © 2009 Société statistique du Canada [source]

    Selecting an optimal cutoff value for creatinine in the model for end-stage liver disease equation

    CLINICAL TRANSPLANTATION, Issue 2 2010
    Teh-Ia Huo
    Huo T-I, Hsu C-Y, Lin H-C, Lee P-C, Lee J-Y, Lee F-Y, Hou M-C, Lee S-D. Selecting an optimal cutoff value for creatinine in the model for end-stage liver disease equation. Clin Transplant 2009 DOI: 10.1111/j.1399-0012.2009.01099.x. © 2009 John Wiley & Sons A/S. Abstract:, Background:, The model for end-stage liver disease (MELD) is used for organ allocation in liver transplantation. The maximal serum creatinine (Cr) level for MELD is set at 4.0 mg/dL; however, there was no outcome data to justify this strategy. Methods:, Ninety-two patients with cirrhosis with Cr level >4 mg/dL were selected from 1438 patients and compared with MELD score-matched controls for three-month and six-month mortality. Results:, At three months, patients with Cr level >4 mg/dL had a significantly higher mortality rate than the 184 controls with a lower Cr level (44.6% vs. 29.3%, p = 0.015). This trend was still significant at six months: the mortality rate was 62% in the index group vs. 45.1% in the control group (p = 0.011). The difference between the index and control groups was the smallest (2.5% at three months and 3.4% at six months) when Cr was up-scaled to 5.5 mg/dL. The predictive accuracy of the MELD was estimated by using area under receiver-operating characteristic (AUC) curve. Only the cutoff of 5.5 mg/dL at six months displayed a higher AUC (0.753). Conclusions:, A cutoff at 5.5 mg/dL may be more appropriate for the MELD. The MELD for patients with cirrhosis with advanced renal insufficiency deserves re-evaluation. [source]

    Performance of diagnostic mammography differs in the United States and Denmark

    INTERNATIONAL JOURNAL OF CANCER, Issue 8 2010
    Allan Jensen
    Abstract Diagnostic mammography is the primary imaging modality to diagnose breast cancer. However, few studies have evaluated variability in diagnostic mammography performance in communities, and none has done so between countries. We compared diagnostic mammography performance in community-based settings in the United States and Denmark. The performance of 93,585 diagnostic mammograms from 180 facilities contributing data to the US Breast Cancer Surveillance Consortium (BCSC) from 1999 to 2001 was compared to that of all 51,313 diagnostic mammograms performed at Danish clinics in 2000. We used the imaging workup's final assessment to determine sensitivity, specificity and an estimate of accuracy: area under the receiver-operating characteristics (ROCs) curve (AUC). Diagnostic mammography had slightly higher sensitivity in the United States (85%) than in Denmark (82%). In contrast, it had higher specificity in Denmark (99%) than in the United States (93%). The AUC was high in both countries: 0.91 in United States and 0.95 in Denmark. Denmark's higher accuracy may result from supplementary ultrasound examinations, which are provided to 74% of Danish women but only 37% to 52% of US women. In addition, Danish mammography facilities specialize in either diagnosis or screening, possibly leading to greater diagnostic mammography expertise in facilities dedicated to symptomatic patients. Performance of community-based diagnostic mammography settings varied markedly between the 2 countries, indicating that it can be further optimized. [source]

    Usefulness of non-invasive markers for predicting liver cirrhosis in patients with chronic hepatitis B

    JOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 1 2010
    Kwang Gyun Lee
    Abstract Background and Aim:, Recently, various non-invasive blood markers and indices have been studied to overcome the limitations of liver biopsy, such as its invasiveness and sampling errors. However, the majority of these studies have focused on patients with chronic hepatitis C. Accordingly, this study was performed to evaluate the significances of various non-invasive serum markers in terms of predicting the presence of liver cirrhosis in chronic hepatitis B. Methods:, We included 125 chronic hepatitis B patients who had undergone liver biopsy. Fibrosis stage was assessed using the METAVIR scoring system (F0,F4), which defines liver cirrhosis as F4. In addition, we measured various blood markers at times of liver biopsy. Results:, Thirty four of the 125 patients (27.2%) were rated as F4 by liver biopsy. Age, platelet, white blood cells, aspartate aminotransferase (AST), alanine aminotransferase, haptoglobin, apolipoprotein-A1 (Apo-A1), collagen-IV, hyaluronic acid, ,2-macroglobulin, matrix metalloproteinase-2, and YKL-40 were significantly different between patients with chronic hepatitis and those with liver cirrhosis. However, multivariate analysis showed that only platelet, AST, haptoglobin, and Apo-A1 independently predicted the presence of liver cirrhosis. Having identified these four factors, we devised a system, which we refer to as platelet count, AST, haptoglobin, and Apo-A1 (PAHA). The area under the receiver-operating characteristics (AUROC) of PAHA indices for the presence of liver cirrhosis was 0.924 (95% confidence interval, 0.877,0.971), which was significantly greater than the AUROC of other indices of fibrosis. Conclusion:, The devised PAHA system was found to be useful for predicting the presence of liver cirrhosis in patients with chronic hepatitis B. [source]